Compost and Your Compost Pile, Part 2 — Composting Structures

Compost is amazing. Of the many gardening activities I participate in, composting is one I am passionate about completely. To take kitchen scraps, weeds, lawn clippings, rotten fruit, coffee grounds, and a myriad of other organic matter and turn it into a compound that magically improves soil and garden productivity, while bypassing the garbage truck and city landfill, is fascinating and rewarding.

I covered the basic process behind composting in my earlier article, “Compost and Your Compost Pile, Part 1“. Today I’ll cover some preliminary steps that will allow you to start your compost pile.

Let’s begin with location and structure. As briefly mentioned in the previous article, locate your compost pile near your garden. If you’ve followed some of my earlier advice, your garden is located close enough to your house that it isn’t a arduous journey to walk to it. Since most of what you’ll add to your pile comes from the garden and kitchen, it makes sense that its location is close to both. One of the reasons for composting is to use the finished compost in your garden soil so it makes sense again to locate it near its ultimate end.

My compost piles near the garden

A well-managed compost pile will not smell bad so you don’t need to worry about sticking it in an out-of-the-way spot to avoid terrible aromas. In fact, finished compost has an earthy, clean, warm smell. My compost piles are always near the garden with enough space in front of them that I can maneuver a wheelbarrow to unload organic refuse and later load up with dark, crumbly compost.

The microorganisms don’t require sunlight to decompose material so you shouldn’t worry about how much shade is on the pile. That is unless you plan to do year-round composting and live in a cold region. Sun will help heat up the pile and in the winter can help keep the pile from freezing; a full-sun location may be preferred. Alternatively if you live in a very dry region locating the pile in the shade may help keep it from drying out too quickly.

The size of your pile is also a factor in determining its location. If you plan to have a single big pile you only need enough space to handle a planned mass with a footprint of about 16 square feet (four feet by four feet). If you want to do a two-pile or three-pile setup, you need to plan for more space, to include paths to and from the piles.

The type of compost pile you have is a factor in selecting the site so let’s discuss structure options for composting. Beyond a single pile resting on the ground, most gardeners use some type of structure. Composting structures are open or closed, with open structures usually being some type of cage or box to hold the pile together and closed structures being a type of container that fully encloses the composting material. I find that open structures allow more flexibility in composting and are often easier to manage.

When I planned my last garden, I laid out the spot for a two-pile system and sank 4×4 posts in the ground. The posts framed two, four feet by four feet areas and rose about five feet above the base soil. I secured four-feet high, plastic garden fencing around and in between the posts to create thin walls. The front was open, though I used extra wire fencing to block it and keep the dogs out of the piles.

My two-pile structure

When we moved to our new house, I set up a compost pile right away, before I knew where the garden would be. For this more mobile, temporary structure I nailed together wooden pallets to frame three walls; another pallet served as a removable front. Later this year, once I finish laying out my vegetable garden and put a fence around it, I’ll build a more permanent three-pile setup from 2×4 lumber closer to the garden.

My simple pallet structure

For a movable structure that can be located directly on a garden plot, I’ve used rigid, four-feet high fencing (metal or plastic). A 12-feet long section formed into a circle with the ends attached together creates a space that is four feet in diameter and four feet in height, perfect for a compost pile. When the compost is finished you simply remove the external fencing and the compost falls directly on the spot where you’ll use it.

My movable fencing structure

The idea behind open structures is to help contain all of the composting material as the mass builds. Whether you use wood, plastic, or metal, the structure creates a framework that supports the size of your pile. The structure can be permanent or temporary. Stacked cinder blocks or bricks can be used to create a compost structure. Stacked bales of straw will contain a pile and will also add some material to the decomposing process. Even walled mounds of soil can form a structure.

Open composting structures have some advantages. You can add material to the pile regularly because the top and sides are often open or easily accessible. The cost of building the framework can be negligible if you re-use the components from other projects, like fencing, cinder blocks, wood, or pallets; even new material isn’t that expensive. Conducting the regular activities of managing the pile (which I’ll cover in another article) is easy because the structure is designed to be accessible. The size of the pile and how much material you compost is flexible; you control the size of the structure. Organisms like beetles and earthworms, important creatures in the decomposition process, are free to enter the pile and do their work. When it comes time to collect the finished compost, all you need is a shovel and wheelbarrow.

Open composting structures have some disadvantages as well. The open structure allows access to animals and pests as well. Exposed to sun and wind, piles tend to dry out quickly and extra water needs to be added to maintain moist conditions. They can be unsightly to some gardeners. Once you start your pile it’s not easy to move it.

The other composting option is a closed structure. A closed composting structure fully contains the composting material. These are often made of plastic and are the ones you see sold as a “composter”. They’re a four-sided box with a lid, a barrel with a trap door, or a big ball with a screw top. Typically you load all of your organic material into the closed structure and leave it until it is fully composted. If it is a barrel system that you hand-turn regularly, there is very little maintenance. If it is a box system you’ll need to add water and air to the material to keep it decomposing.

My closed structure

The advantages and disadvantages of closed structure are nearly opposite those of an open structure. Because the access is usually through a single opening, it isn’t as accessible. The cost of most closed structures is higher and can be quite expensive (unless you just use a heavy duty trash bag as the container). Managing the pile (adding water and aerating) can be difficult without special tools. Many structures sold in stores are too small to build sufficient mass and the material takes a very long time to decompose. Only bacteria is at work because other microorganisms and insects don’t have access to the pile. Collecting the finished compost can be difficult because of the limited single-door access.

On the flip side, they’re very effective at keeping animals from the pile, they don’t dry out as quickly, they are orderly, and can be aesthetically pleasing. They’re also highly portable so you can change locations easily.

You might ascertain that I prefer open structures. I do. My first foray into composting was with a plastic closed system that I purchased (not inexpensively) from our local utilities company. I filled it from the small opening at the top, layered greens and browns, kept it as moist as I could (which was hard to determine due to the closed sides), and tried to add air to the material. The width of the square base was less than two feet on each side; it was just over three feet tall. After two years of regular attention, the material didn’t look anything like compost. I know many other gardeners who tried these small tower composters and had similar results. I don’t recommend them.

The type I don't recommend

The big barrel composters, or “tumblers”, that you hand rotate do work pretty well. They hold a good mass of material, are efficient at maintaining moisture levels, and add oxygen when you rotate them. Their trapdoor design that can make unloading the finished compost tricky. The biggest critique is the cost; they can be very expensive. If you can afford it and don’t like getting your hands dirty, this may be the system for you.

With open structures, you’ll need to add water regularly because they dry out so consider locating them in a spot that has easy access to a water source. With closed structures, particularly the big barrels, you won’t need to add as much water so you can locate them just about anywhere; they can be placed just outside your back door.

I like connecting with the soil and my plants and I think of compost the same way. Seeing the colors change during decomposition, sticking my hand in the pile to see if it’s warm, and feeling the finished product all add to the sensory pleasure of gardening. Open structures give me more feedback about the process.

In my next couple articles I’ll continue with information about managing a compost pile. It’s not hard, but it does take some work.